Vascular endothelial growth factor in amyotrophic lateral sclerosis and other neurodegenerative diseases

Human Glial Cells as Innovative Targets for the Therapy of Central Nervous System Pathologies

In vitro and preclinical in vivo research in the last 35 years has clearly highlighted the crucial physiopathological role of glial cells, namely astrocytes/microglia/oligodendrocytes and satellite glial cells/Schwann cells in the central and peripheral nervous system, respectively. Several possible pharmacological targets to various neurodegenerative disorders and painful conditions have therefore been successfully identified, including receptors and enzymes, and mediators of neuroinflammation. However, the translation of these promising data to a clinical setting is often hampered by both technical and biological difficulties, making it necessary to perform experiments on human cells and models of the various diseases. In this review we will, therefore, summarize the most relevant data on the contribution of glial cells to human pathologies and on their possible pharmacological modulation based on data obtained in post-mortem tissues and in iPSC-derived human brain cells and organoids. The possibility of an in vivo visualization of glia reaction to neuroinflammation in patients will be also discussed.

TDP-43 protein interactome informs about perturbed canonical pathways and may help develop personalized medicine approaches for patients with TDP-43 pathology

Transactive response DNA binding protein of 43 kDa (TDP-43) pathology is a common proteinopathy observed among a broad spectrum of patients with neurodegenerative disease, regardless of the mutation. This suggests that protein-protein interactions of TDP-43 with other proteins may in part be responsible for the pathology. To gain better insights, we investigated TDP-43-binding proteins in each domain and correlated these interactions with canonical pathways. These investigations revealed key cellular events that are involved and are important at each domain and suggested previously identified compounds to modulate key aspects of these canonical pathways. Our approach proposes that personalized medicine approaches, which focus on perturbed cellular mechanisms would be feasible in the near future.

Insights on the Multifaceted Roles of Wild-Type and Mutated Superoxide Dismutase 1 in Amyotrophic Lateral Sclerosis Pathogenesis

Amyotrophic Lateral Sclerosis (ALS) is a progressive motor neurodegenerative disease. Cell damage in ALS is the result of many different, largely unknown, pathogenetic mechanisms. Astrocytes and microglial cells play a critical role also for their ability to enhance a deranged inflammatory response. Excitotoxicity, due to excessive glutamate levels and increased intracellular Ca2+ concentration, has also been proposed to play a key role in ALS pathogenesis/progression. Reactive Oxygen Species (ROS) behave as key second messengers for multiple receptor/ligand interactions. ROS-dependent regulatory networks are usually mediated by peroxides. Superoxide Dismutase 1 (SOD1) physiologically mediates intracellular peroxide generation. About 10% of ALS subjects show a familial disease associated with different gain-of-function SOD1 mutations. The occurrence of sporadic ALS, not clearly associated with SOD1 defects, has been also described. SOD1-dependent pathways have been involved in neuron functional network as well as in immune-response regulation. Both, neuron depolarization and antigen-dependent T-cell activation mediate SOD1 exocytosis, inducing increased interaction of the enzyme with a complex molecular network involved in the regulation of neuron functional activity and immune response. Here, alteration of SOD1-dependent pathways mediating increased intracellular Ca2+ levels, altered mitochondria functions and defective inflammatory process regulation have been proposed to be relevant for ALS pathogenesis/progression.

Effect of Moringa oleifera leaf extract on exercise and dexamethasone-induced functional impairment in skeletal muscles

Background

Chronic administration of steroids like dexamethasone produces symptoms including weight loss and skeletal muscle dysfunction. Similar events are reported in chronic or high-intensity exercises, that can lead to fatigue and muscle damage.

Objective

In the present study, the effect of Moringa oleifera leaf extract was evaluated against dexamethasone (Dex) and exercise (Exe)-induced muscle changes in rats.

Materials and methods

Six groups each containing 6 rats, namely normal, Dex control, Exe Control, Dex + M. oleifera leaf extract (300mg/kgp.o.), Dex + Exe, Dex + Exe + M. oleifera leaf extract were assessed in the study. Dex was administered at 0.6 mg/kg i.p. daily for 7 days. Exercise was given for a total of 10 days after 30 minutes of dosing using treadmill equipment for 900 seconds at speed 18 m/min. Animals were assessed for variation in body weight, muscular endurance using treadmill, locomotor activity using actophotometer, motor coordination using rotarod on day zero, and day seven. Hemidiaphragm of rats were isolated and used for evaluation of the glucose uptake. Gastrocnemius muscle was isolated and subjected to hematoxylin and eosin staining.

Results

Dex and Exe control animals showed a significant decrease in skeletal muscle activity when compared to normal control animals in the actophotometer test. Improvement in endurance were seen in Dex + M. oleifera leaf extract, and Dex + exercise + M. oleifera leaf extract groups compared to Dex control group. Improvement in locomotor activity was seen in Dex group subjected to exercise and was significant when treated with M. oleifera leaf extract. Histology reports were in accordance with the functional parameters.

Conclusion

M. oleifera leaf extract supplemented with exercise showed a reversal in the dexamethasone-induced functional impairment in skeletal muscles.

Adipose-derived stem cells protect motor neurons and reduce glial activation in both in vitro and in vivo models of ALS

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative condition for which new therapeutic options are urgently needed. We injected GFP⁺ adipose-derived stem cells (EGFP-ADSCs) directly into the cerebrospinal fluid (CSF) of transgenic SOD1^G93A mice, a well-characterized model of familial ALS. Despite short-term survival of the injected cells and limited engraftment efficiency, EGFP-ADSCs improved motor function and delayed disease onset by promoting motor neuron (MN) survival and reducing glial activation. We then tested the in vitro neuroprotective potential of mouse ADSCs in astrocyte/MN co-cultures where ALS astrocytes show neurotoxicity. ADSCs were able to rescue MN death caused by ALS astrocytes derived from symptomatic SOD1^G93A mice. Further, ADSCs were found to reduce the inflammatory signature of ALS astrocytes by inhibiting the release of pro-inflammatory mediators and inducing the secretion of neuroprotective factors. Finally, mouse ADSCs were able to protect MNs from the neurotoxicity mediated by human induced astrocytes (iAstrocytes) derived from patients with either sporadic or familial ALS, thus for the first time showing the potential therapeutic translation of ADSCs across the spectrum of human ALS. These data in two translational models of ALS show that, through paracrine mechanisms, ADSCs support MN survival and modulate the toxic microenvironment that contributes to neurodegeneration in ALS.

Neuroprotective Effect of Vascular Endothelial Growth Factor on Motoneurons of the Oculomotor System

Vascular endothelial growth factor (VEGF) was initially characterized as a potent angiogenic factor based on its activity on the vascular system. However, it is now well established that VEGF also plays a crucial role as a neuroprotective factor in the nervous system. A deficit of VEGF has been related to motoneuronal degeneration, such as that occurring in amyotrophic lateral sclerosis (ALS). Strikingly, motoneurons of the oculomotor system show lesser vulnerability to neurodegeneration in ALS compared to other motoneurons. These motoneurons presented higher amounts of VEGF and its receptor Flk-1 than other brainstem pools. That higher VEGF level could be due to an enhanced retrograde input from their target muscles, but it can also be produced by the motoneurons themselves and act in an autocrine way. By contrast, VEGF’s paracrine supply from the vicinity cells, such as glial cells, seems to represent a minor source of VEGF for brainstem motoneurons. In addition, ocular motoneurons experiment an increase in VEGF and Flk-1 level in response to axotomy, not observed in facial or hypoglossal motoneurons. Therefore, in this review, we summarize the differences in VEGF availability that could contribute to the higher resistance of extraocular motoneurons to injury and neurodegenerative diseases.

Intracerebroventricular delivery of vascular endothelial growth factor in patients with amyotrophic lateral sclerosis, a phase I study

We studied the feasibility, safety, tolerability and pharmacokinetics of intracerebroventricular delivery of recombinant human vascular endothelial growth factor in patients with amyotrophic lateral sclerosis. In this phase I study in patients with amyotrophic lateral sclerosis, the study drug was delivered using an implantable programmable pump connected to a catheter inserted in the frontal horn of the lateral cerebral ventricle. A first cohort received open label vascular endothelial growth factor (0.2, 0.8 and 2 µg/day), a second cohort received placebo, 0.8 or 2 µg/day of study dug. After the 3-month study period, all patients could participate in an open label extension study. In total, 18 patients with amyotrophic lateral sclerosis, seen at the University Hospitals in Leuven were included. The surgical procedure was well tolerated in most patients. One patient had transient postoperative seizures, due to an ischemic lesion along the catheter tract. The first 3-month study period was completed by 15/18 patients. Administration of 2 µg/day vascular endothelial growth factor resulted in sustained detectable levels in cerebrospinal fluid. A pulmonary embolus occurred in 3 patients, in 1 patient in the first 3-month study, and in 2 patients during the open label extension study. The study drug was well tolerated in the other patients, for up to 6 years in the open label extension study. Our study shows that intracerebroventricular administration of 2 µg/day of vascular endothelial growth factor to patients with amyotrophic lateral sclerosis is feasible, results in detectable cerebrospinal fluid levels and is well tolerated in most patients. The most common serious adverse event was a pulmonary embolus.

Sources and lesion-induced changes of VEGF expression in brainstem motoneurons

Motoneurons of the oculomotor system show lesser vulnerability to neurodegeneration compared to other cranial motoneurons, as seen in amyotrophic lateral sclerosis (ALS). The overexpression of vascular endothelial growth factor (VEGF) is involved in motoneuronal protection. As previously shown, motoneurons innervating extraocular muscles present a higher amount of VEGF and its receptor Flk-1 compared to facial or hypoglossal motoneurons. Therefore, we aimed to study the possible sources of VEGF to brainstem motoneurons, such as glial cells and target muscles. We also studied the regulation of VEGF in response to axotomy in ocular, facial, and hypoglossal motor nuclei. Basal VEGF expression in astrocytes and microglial cells of the cranial motor nuclei was low. Although the presence of VEGF in the different target muscles for brainstem motoneurons was similar, the presynaptic element of the ocular neuromuscular junction showed higher amounts of Flk-1, which could result in greater efficiency in the capture of the factor by oculomotor neurons. Seven days after axotomy, a clear glial reaction was observed in all the brainstem nuclei, but the levels of the neurotrophic factor remained low in glial cells. Only the injured motoneurons of the oculomotor system showed an increase in VEGF and Flk-1, but such an increase was not detected in axotomized facial or hypoglossal motoneurons. Taken together, our findings suggest that the ocular motoneurons themselves upregulate VEGF expression in response to lesion. In conclusion, the low VEGF expression observed in glial cells suggests that these cells are not the main source of VEGF for brainstem motoneurons. Therefore, the higher VEGF expression observed in motoneurons innervating extraocular muscles is likely due either to the fact that this factor is more avidly taken up from the target muscles, in basal conditions, or is produced by these motoneurons themselves, and acts in an autocrine manner after axotomy.

Acute Methylmercury Exposure and the Hypoxia-Inducible Factor-1α Signaling Pathway under Normoxic Conditions in the Rat Brain and Astrocytes in Vitro

BACKGROUND

As a ubiquitous environmental pollutant, methylmercury (MeHg) induces toxic effects in the nervous system, one of its main targets. However, the exact mechanisms of its neurotoxicity have not been fully elucidated. Hypoxia-inducible factor- 1 α (HIF- 1 α ), a transcription factor, plays a crucial role in adaptive and cytoprotective responses in cells and is involved in cell survival, proliferation, apoptosis, inflammation, angiogenesis, glucose metabolism, erythropoiesis, and other physiological activities.

OBJECTIVES

The aim of this study was to explore the role of HIF- 1 α in response to acute MeHg exposure in rat brain and primary cultured astrocytes to improve understanding of the mechanisms of MeHg-induced neurotoxicity and the development of effective neuroprotective strategies.

METHODS

Primary rat astrocytes were treated with MeHg (0 - 10 μ M ) for 0.5 h . Cell proliferation and cytotoxicity were assessed with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl diphenyltetrazolium bromide (MTT) assay and a lactate dehydrogenase (LDH) release assay, respectively. Reactive oxygen species (ROS) levels were analyzed to assess the level of oxidative stress using 2',7'-dichlorofluorescin diacetate (DCFH-DA) fluorescence. HIF- 1 α , and its downstream proteins, glucose transporter 1 (GLUT-1), erythropoietin (EPO), and vascular endothelial growth factor A (VEGF-A) were analyzed by means of Western blotting. Real-time PCR was used to detect the expression of HIF- 1 α mRNA. Pretreatment with protein synthesis inhibitor (CHX), proteasome inhibitor (MG132), or proline hydroxylase inhibitor (DHB) were applied to explore the possible mechanisms of HIF- 1 α inhibition by MeHg. To investigate the role of HIF- 1 α in MeHg-induced neurotoxicity, cobalt chloride (CoC l 2 ), 2-methoxyestradiol (2-MeOE2), small interfering RNA (siRNA) transfection and adenovirus overexpression were used. Pretreatment with N-acetyl-L-cysteine (NAC) and vitamin E (Trolox) were used to investigate the putative role of oxidative stress in MeHg-induced alterations in HIF- 1 α levels. The expression of HIF- 1 α and related downstream proteins was detected in adult rat brain exposed to MeHg (0 - 10 mg / kg ) for 0.5 h in vivo.

RESULTS

MeHg caused lower cell proliferation and higher cytotoxicity in primary rat astrocytes in a time- and concentration-dependent manner. In comparison with the control cells, exposure to 10 μ M MeHg for 0.5 h significantly inhibited the expression of astrocytic HIF- 1 α , and the downstream genes GLUT-1, EPO, and VEGF-A (p < 0.05 ), in the absence of a significant decrease in HIF- 1 α mRNA levels. When protein synthesis was inhibited by CHX, MeHg promoted the degradation rate of HIF- 1 α . MG132 and DHB significantly blocked the MeHg-induced decrease in HIF- 1 α expression (p < 0.05 ). Overexpression of HIF- 1 α significantly attenuated the decline in MeHg-induced cell proliferation, whereas the inhibition of HIF- 1 α significantly increased the decline in cell proliferation (p < 0.05 ). NAC and Trolox, two established antioxidants, reversed the MeHg-induced decline in HIF- 1 α protein levels and the decrease in cell proliferation (p < 0.05 ). MeHg suppressed the expression of HIF- 1 α and related downstream target proteins in adult rat brain.

DISCUSSION

MeHg induced a significant reduction in HIF- 1 α protein by activating proline hydroxylase (PHD) and the ubiquitin proteasome system (UPS) in primary rat astrocytes. Additionally, ROS scavenging by antioxidants played a neuroprotective role via increasing HIF- 1 α expression in response to MeHg toxicity. Moreover, we established that up-regulation of HIF- 1 α might serve to mitigate the acute toxicity of MeHg in astrocytes, affording a novel therapeutic target for future exploration. https://doi.org/10.1289/EHP5139.

Hypoxia-inducible factors as neuroprotective agent in Alzheimer's disease

Beta amyloid (Aβ)-42 peptide and phosphorylated tau protein have been demonstrated as the pathological hallmarks of Alzheimer's disease (AD). A gradual decline of oxygen and glucose supply to the brain during aging or hypoxia was manifested as a contributing factor to hypometabolism. The brain regions susceptible to hypometabolism are the hippocampus, entorhinal cortex and cognition-associated neocortical regions like parietal, temporal and frontal cortex. In AD patients, the brain regions with hypometabolism can trigger overexpression of amyloid precursor protein and decrease the clearance of Aβ. Aβ and hypoxia can evoke inflammation, oxidative stress and finally neuronal cell death. Among the transcription factors involved in the compensatory mechanism, hypoxia-inducible factor-1 alpha (HIF-1α) has a major role in the cellular adaptation by inducing the expression of several proteins, including vascular endothelial growth factor, erythropoietin and inducible nitric oxide synthase. Therefore, maintaining the HIF-1α level by inhibiting the prolyl 4-hydroxylase was effective to attenuate the nerve damage during hypoxia and postpone the incidence of AD. Agents such as iron chelators, and heavy metals like cobalt and nickel were demonstrated to be effective in maintaining the HIF-1α level in the nerve. This review article discusses the possible role of HIF-1α as a neuroprotector in AD and the future perspectives.

Cerebrospinal fluid biomarkers of neurovascular dysfunction in mild dementia and Alzheimer's disease

Alzheimer's disease (AD) is the most common form of age-related dementias. In addition to genetics, environment, and lifestyle, growing evidence supports vascular contributions to dementias including dementia because of AD. Alzheimer's disease affects multiple cell types within the neurovascular unit (NVU), including brain vascular cells (endothelial cells, pericytes, and vascular smooth muscle cells), glial cells (astrocytes and microglia), and neurons. Thus, identifying and integrating biomarkers of the NVU cell-specific responses and injury with established AD biomarkers, amyloid-β (Aβ) and tau, has a potential to contribute to better understanding of the disease process in dementias including AD. Here, we discuss the existing literature on cerebrospinal fluid biomarkers of the NVU cell-specific responses during early stages of dementia and AD. We suggest that the clinical usefulness of established AD biomarkers, Aβ and tau, could be further improved by developing an algorithm that will incorporate biomarkers of the NVU cell-specific responses and injury. Such biomarker algorithm could aid in early detection and intervention as well as identify novel treatment targets to delay disease onset, slow progression, and/or prevent AD.

Developments in treatments for amyotrophic lateral sclerosis via intracerebroventricular or intrathecal delivery

INTRODUCTION

Amyotrophic lateral scleroses (ALS) are neurodegenerative disorders primarily affecting the motor system. These incurable disorders are relentlessly progressive and typically limit survival to 2 - 5 years after disease onset. An improved knowledge about disease-causing genes, disease proteins and pathways has revealed considerable heterogeneity in ALS. Novel targeted therapies are being developed, but getting these beyond the BBB remains a challenge.

AREAS COVERED

The authors review the intracerebroventricular and intrathecal delivery of drugs for the treatment of ALS in preclinical and clinical studies.

EXPERT OPINION

Lack of BBB permeability should not hold back the development of promising treatments for ALS, as the available evidence suggest that direct intrathecal or intracerebroventricular administration of drug is a feasible delivery route in patients with ALS.

Roles of vascular endothelial growth factor in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal devastating neurodegenerative disorder, involving progressive degeneration of motor neurons in spinal cord, brainstem, and motor cortex. Riluzole is the only drug approved in ALS but it only confers a modest improvement in survival. In spite of a high number of clinical trials no other drug has proved effectiveness. Recent studies support that vascular endothelial growth factor (VEGF), originally described as a key angiogenic factor, also plays a key role in the nervous system, including neurogenesis, neuronal survival, neuronal migration, and axon guidance. VEGF has been used in exploratory clinical studies with promising results in ALS and other neurological disorders. Although VEGF is a very promising compound, translating the basic science breakthroughs into clinical practice is the major challenge ahead. VEGF-B, presenting a single safety profile, protects motor neurons from degeneration in ALS animal models and, therefore, it will be particularly interesting to test its effects in ALS patients. In the present paper the authors make a brief description of the molecular properties of VEGF and its receptors and review its different features and therapeutic potential in the nervous system/neurodegenerative disease, particularly in ALS.

Cellular and molecular mechanisms involved in the neuroprotective effects of VEGF on motoneurons

Vascular endothelial growth factor (VEGF), originally described as a factor with a regulatory role in vascular growth and development, it is also known for its direct effects on neuronal cells. The discovery in the past decade that transgenic mice expressing reduced levels of VEGF developed late-onset motoneuron pathology, reminiscent of amyotrophic lateral sclerosis (ALS), opened a new field of research on this disease. VEGF has been shown to protect motoneurons from excitotoxic death, which is a relevant mechanism involved in motoneuron degeneration in ALS. Thus, VEGF delays motoneuron degeneration and increases survival in animal models of ALS. VEGF exerts its anti-excitotoxic effects on motoneurons through molecular mechanisms involving the VEGF receptor-2 resulting in the activation of the PI3-K/Akt signaling pathway, upregulation of GluR2 subunit of AMPA receptors, inhibition of p38MAPK, and induction of the anti-apoptotic molecule Bcl-2. In addition, VEGF acts on astrocytes to reduce astroglial activation and to induce the release of growth factors. The potential use of VEGF as a therapeutic tool in ALS is counteracted by its vascular effects and by its short effective time frame. More studies are needed to assess the optimal isoform, route of administration, and time frame for using VEGF in the treatment of ALS.

Hypoxia inducible factor-1 as a target for neurodegenerative diseases

Hypoxia inducible factor-1 (HIF-1) is a transcriptional factor responsible for cellular and tissue adaption to low oxygen tension. HIF-1, a heterodimer consisting of a constitutively expressed β subunit and an oxygen-regulated α subunit, regulates a series of genes that participate in angiogenesis, iron metabolism, glucose metabolism, and cell proliferation/survival. The activity of HIF-1 is controlled by post-translational modifications on different amino acid residues of its subunits, mainly the alpha subunit. Besides in ischemic stroke (see review [1]), emerging evidence has revealed that HIF-1 activity and expression of its down-stream genes, such as vascular endothelial growth factor and erythropoietin, are altered in a range of neurodegenerative diseases. At the same time, experimental and clinical evidence has demonstrated that regulating HIF-1 might ameliorate the cellular and tissue damage in the neurodegenerative diseases. These new findings suggest HIF-1 as a potential medicinal target for the neurodegenerative diseases. This review focuses on HIF-1α protein modifications and HIF-1's potential neuroprotective roles in Alzheimer's (AD), Parkinson's (PD), Huntington's diseases (HD), and amyotrophic lateral sclerosis (ALS).

Intramuscular administration of a VEGF zinc finger transcription factor activator (VEGF-ZFP-TF) improves functional outcomes in SOD1 rats

Amyotrophic lateral sclerosis (ALS) is characterized by motor neuron loss leading to paralysis and death. Vascular endothelial growth factor (VEGF) has angiogenic, neurotrophic, and neuroprotective properties, and has preserved neuromuscular function and protected motor neurons in rats engineered to overexpress the human gene coding the mutated G93A form of the superoxide dismutase-1 (SOD1). We assessed the effects of intramuscular administration of a plasmid that encodes a zinc finger protein transcription factor (ZFP-TF) engineered to induce VEGF expression in the SOD1 rat model of ALS. Weekly injections of the plasmid preserved ipsilateral hindlimb grip strength and markedly improved rotarod performance in SOD1 rats compared to the vehicle-treated group. The number of motor neurons and the proportion of innervated neuromuscular junctions were similar in both groups. In conclusion, our data suggest that administration of the VEGF-ZFP-TF may be neuroprotective and has potential as a safe and practical approach for the management of motor disability in ALS.

alpha-Tocopheryl phosphate--an active lipid mediator?

The vitamin E (alpha-tocopherol, alphaT) derivative, alpha-tocopheryl phosphate (alphaTP), is detectable in small amounts in plasma, tissues, and cultured cells. Studies done in vitro and in vivo suggest that alphaT can become phosphorylated and alphaTP dephosphorylated, suggesting the existence of enzyme(s) with alphaT kinase or alphaTP phosphatase activity, respectively. As a supplement in animal studies, alphaTP can reach plasma concentrations similar to alphaT and only a part is dephosphorylated; thus, alphaTP may act both as pro-vitamin E, but also as phosphorylated form of vitamin E with possibly novel regulatory activities. Many effects of alphaTP have been described: in the test tube alphaTP modulates the activity of several enzymes; in cell culture alphaTP affects proliferation, apoptosis, signal transduction, and gene expression; in animal studies alphaTP prevents atherosclerosis, ischemia/reperfusion injury, and induces hippocampal long-term potentiation. At the molecular level, alphaTP may act as a cofactor for enzymes, as an active lipid mediator similar to other phosphorylated lipids, or indirectly by altering membrane characteristics such as lipid rafts, fluidity, and curvature. In this review, the molecular and cellular activities of alphaTP are examined and the possible functions of alphaTP as a natural compound, cofactor and active lipid mediator involved in signal transduction and gene expression discussed.

The neurobiology of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a degenerative disease affecting the motor neurons. In spite of our growing insights into its biology, it remains a lethal condition. The identification of the cause of several of the familial forms of ALS allowed generation of models to study this disease both in vitro and in vivo. Here, we summarize what is known about the pathogenic mechanisms of ALS induced by hereditary mutations, and attempt to identify the relevance of these findings for understanding the pathogenic mechanisms of the sporadic form of this disease.

VEGF-A165b is cytoprotective and antiangiogenic in the retina

PURPOSE

A number of key ocular diseases, including diabetic retinopathy and age-related macular degeneration, are characterized by localized areas of epithelial or endothelial damage, which can ultimately result in the growth of fragile new blood vessels, vitreous hemorrhage, and retinal detachment. VEGF-A(165), the principal neovascular agent in ocular angiogenic conditions, is formed by proximal splice site selection in its terminal exon 8. Alternative splicing of this exon results in an antiangiogenic isoform, VEGF-A(165)b, which is downregulated in diabetic retinopathy. Here the authors investigate the antiangiogenic activity of VEGF(165)b and its effect on retinal epithelial and endothelial cell survival.

METHODS

VEGF-A(165)b was injected intraocularly in a mouse model of retinal neovascularization (oxygen-induced retinopathy [OIR]). Cytotoxicity and cell migration assays were used to determine the effect of VEGF-A(165)b.

RESULTS

VEGF-A(165)b dose dependently inhibited angiogenesis (IC(50), 12.6 pg/eye) and retinal endothelial migration induced by 1 nM VEGF-A(165) across monolayers in culture (IC(50), 1 nM). However, it also acts as a survival factor for endothelial cells and retinal epithelial cells through VEGFR2 and can stimulate downstream signaling. Furthermore, VEGF-A(165)b injection, while inhibiting neovascular proliferation in the eye, reduced the ischemic insult in OIR (IC(50), 2.6 pg/eye). Unlike bevacizumab, pegaptanib did not interact directly with VEGF-A(165)b.

CONCLUSIONS

The survival effects of VEGF-A(165)b signaling can protect the retina from ischemic damage. These results suggest that VEGF-A(165)b may be a useful therapeutic agent in ischemia-induced angiogenesis and a cytoprotective agent for retinal pigment epithelial cells.

The application of platelet-rich plasma may be a novel treatment for central nervous system diseases

As a potential biological product, platelet-rich plasma (PRP) has been widely utilized in the areas of oral and maxillofacial reconstruction, bone and soft tissue restoration and wound healing. A recent study reported that the application of PRP on interrupted sciatic nerve could promote remyelinization of peripheral nerve. This renovated a notion that the application of PRP might extend to the nervous system. Most central nervous system (CNS) diseases have a series of common pathological changes in the later period of diseases which induce neurons and glia apoptosis and aggravate neurological dysfunction. It has been demonstrated that the potent restorative function of PRP is mainly based on neurotrophic capacity of preparation rich in growth factors (PRGFs) and scaffolding effect of platelet-rich gel (PRG), all of which could be certified to ameliorate the pathological process of CNS diseases. In view of this, we propose a hypothesis that the application of PRP and its derivatives might provide a novel therapeutic approach for CNS diseases, especially for traumatic brain or spinal cord injury, autoimmune diseases and neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis.

Neural stem cell transplantation can ameliorate the phenotype of a mouse model of spinal muscular atrophy

Spinal muscular atrophy (SMA), a motor neuron disease (MND) and one of the most common genetic causes of infant mortality, currently has no cure. Patients with SMA exhibit muscle weakness and hypotonia. Stem cell transplantation is a potential therapeutic strategy for SMA and other MNDs. In this study, we isolated spinal cord neural stem cells (NSCs) from mice expressing green fluorescent protein only in motor neurons and assessed their therapeutic effects on the phenotype of SMA mice. Intrathecally grafted NSCs migrated into the parenchyma and generated a small proportion of motor neurons. Treated SMA mice exhibited improved neuromuscular function, increased life span, and improved motor unit pathology. Global gene expression analysis of laser-capture-microdissected motor neurons from treated mice showed that the major effect of NSC transplantation was modification of the SMA phenotype toward the wild-type pattern, including changes in RNA metabolism proteins, cell cycle proteins, and actin-binding proteins. NSC transplantation positively affected the SMA disease phenotype, indicating that transplantation of NSCs may be a possible treatment for SMA.

VEGF and ALS

In amyotrophic lateral sclerosis (ALS), an adult-onset progressive degeneration of motor neurons occurring as sporadic and familial disease, there is emerging evidence for and against the role of vascular endothelial growth factor (VEGF), an endothelial cell mitogen crucial for angiogenesis, in its etiopathogenesis. Our understanding of the role of VEGF in ALS has come from studies of both experimental models and human cases. In this article, I have examined in detail the in vitro and in vivo evidence for and against VEGF in ALS, concluding that more compelling evidence is required before we can conclusively link VEGF to ALS in humans.

Amyotrophic lateral sclerosis: from current developments in the laboratory to clinical implications

Amyotrophic lateral sclerosis (ALS) is a late-onset progressive degeneration of motor neurons occurring both as a sporadic and a familial disease. The etiology of ALS remains unknown, but one fifth of instances are due to specific gene defects, the best characterized of which is point mutations in the gene coding for Cu/Zn superoxide dismutase (SOD1). Because sporadic and familial ALS affect the same neurons with similar pathology, it is hoped that understanding these gene defects will help in devising therapies effective in both forms. A wealth of evidence has been collected in rodents made transgenic for mutant SOD1, which represent the best available models for familial ALS. Mutant SOD1 likely induces selective vulnerability of motor neurons through a combination of several mechanisms, including protein misfolding, mitochondrial dysfunction, oxidative damage, cytoskeletal abnormalities and defective axonal transport, excitotoxicity, inadequate growth factor signaling, and inflammation. Damage within motor neurons is enhanced by noxious signals originating from nonneuronal neighboring cells, where mutant SOD1 induces an inflammatory response that accelerates disease progression. The clinical implication of these findings is that promising therapeutic approaches can be derived from multidrug treatments aimed at the simultaneous interception of damage in both motor neurons and nonmotor neuronal cells.

VEGF reduces astrogliosis and preserves neuromuscular junctions in ALS transgenic mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease resulting from motor neuron loss in the spinal cord and brain stem. In the present study, we found that systemic administration of recombinant vascular endothelial growth factor (VEGF) significantly diminished astrogliosis and increased the number of neuromuscular junctions in a Cu/Zn superoxide dismutase (SOD1) transgenic mouse model of ALS. Our results thus demonstrate a novel regulatory role of VEGF on astrocytes and are suggestive of protective effects of VEGF both in the peripheral and central nervous system in the SOD1 transgenic mouse model. These findings warrant further evaluation of the mechanism(s) of regulatory effects of VEGF on neuronal and non-neuronal cells, and the relation of these events to motor neuron degeneration and the onset and progression of ALS.

Vascular endothelial growth factor receptor-2: structure, function, intracellular signalling and therapeutic inhibition

Vascular endothelial growth factors (VEGFs) regulate vascular development, angiogenesis and lymphangiogenesis by binding to a number of receptors. VEGFR-1 is required for the recruitment of haematopoietic stem cells and the migration of monocytes and macrophages, VEGFR-2 regulates vascular endothelial function and VEGFR-3 regulates lymphatic endothelial cell function. Over the last decade, considerable progress has been made in delineating the VEGFR-2 specific intracellular signalling cascades leading to proliferation, migration, survival and increased permeability, each of which contributes to the angiogenic response. Furthermore, therapeutic inhibition of VEGFR-2 action is now having an impact in the clinic for the treatment of a number of diseases.

Amyotrophic lateral sclerosis: all roads lead to Rome

Amyotrophic lateral sclerosis (ALS) is the most frequent adult-onset motor neuron disease characterized by degeneration of upper and lower motor neurons, generalized weakness and muscle atrophy. Most cases of ALS appear sporadically but some forms of the disease result from mutations in the gene encoding the antioxidant enzyme Cu/Zn superoxide dismutase (SOD1). Several other mutated genes have also been found to predispose to ALS including, among others, one that encodes the regulator of axonal retrograde transport dynactin. As all roads lead to the proverbial Rome, we discuss here how distinct molecular pathways may converge to the same final result that is motor neuron death. We critically review the basic research on SOD1-linked ALS to propose a pioneering model of a 'systemic' form of the disease, causally involving multiple cell types, either neuronal or non-neuronal. Contrasting this, we also postulate that other neuron-specific defects, as those triggered by dynactin dysfunction, may account for a primary motor neuron disease that would represent 'pure' neuronal forms of ALS. Identifying different disease subtypes is an unavoidable step toward the understanding of the physiopathology of ALS and will hopefully help to design specific treatments for each subset of patients.